Enhanced switched balancing network for battery pack

ABSTRACT

One or more of the present embodiments provide for a battery cell balancing system and strategy that delivers more efficient use of battery capacities as needed for different use cases. For example, a balancing circuit is provided to support targeted battery cell passive and active balancing according to a balancing strategy for the use cases. Further the balancing circuit allows for cell balancing to be performed while the battery cells are collectively being charged or discharged.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/213,155, filed Mar. 25, 2021, which a continuation of U.S. patentapplication Ser. No. 16/101,032, filed Aug. 10, 2018, each of which ishereby incorporated by reference.

FIELD

This application relates to enhanced switched balancing networks forbalancing battery cells.

BACKGROUND

High performance battery systems have been developed and deployed fordifferent use-case applications, such as for grid and microgrid energystorage and management, and for renewable energy integration (e.g.,solar, wind, hydro, etc.). For example, solar energy may be collectedand stored in the battery systems for use during high energy consumptiontimes, such as during summer months when energy demands forair-conditioning are well above average. To maximize the capacity of thebattery systems and to utilize the battery systems safely, batterybalancing techniques and strategies have been deployed. For example,when battery cell voltages dip below a lower limit, the battery cellsbecome a fire hazard and must be discarded. Likewise, if battery cellsare overcharged and the battery cell voltages rise above an upper limit,the battery cells also become a fire hazard.

Various active and passive balancing techniques have been developed toallow for more of a battery to be used when charging and discharging,and to increase safety. However, there are costs to active and passivebalancing. For example, passive balancing discards energy by dischargingbattery cells that are above a threshold with respect to an average cellvoltage, leading to parasitic and efficiency losses. Active balancingoften uses low efficiency components to charge, leading to even greaterefficiency losses. Although various balancing strategies have beendeveloped, the balancing strategy is deployed as a static decision formost battery systems, such as deploying simple balancing techniques tobalance cell voltages to an average cell voltage for all cells orbalancing to a target voltage. However, different use cases could beimproved by employing more efficient and robust balancing strategies.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

One or more of the present embodiments provide for a battery cellbalancing system and strategy that delivers more efficient use ofbattery capacities as needed for different use cases. For example, abalancing circuit is provided to support targeted battery cell passiveand active balancing according to a balancing strategy for the usecases. Further the balancing circuit allows for cell balancing to beperformed while the battery cells are collectively being charged ordischarged.

Further, instead of having a static, single balancing strategy, one ormore the present embodiments provide for a suite of preset andcustomizable balancing applications that can be configured, selected andimplemented to match the requirements of a present use case. The suiteof preset and customizable balancing applications may be presented toand selected by a user to tailor the balancing system to a particularuse case. Alternatively, the balancing system may automatically select abalancing application, such as based on one or more inputs, to tailorthe balancing system to the present use case.

In one embodiment, a balancing circuit is provided. The balancingcircuit includes a voltage source coupled to the balancing circuit via acharge balancing relay and a load coupled to the balancing circuit via adischarge balancing relay. The balancing circuit further includes aplurality of cell group controllers, with each of the plurality of cellgroup controllers configured to couple one of a plurality of cell groupsto the balancing circuit via one of a plurality of cell group balancingrelays. The balancing controller is also configured to balance theplurality of cell groups by controlling the charge balancing relay, thedischarge balancing relay and the plurality of cell controllers.

In a further embodiment, another balancing circuit is provided. Thebalancing circuit includes a plurality of cell group stacks and aplurality of stack controllers. Each cell group stack includes aplurality of cell groups and a plurality of balancing controllers.Further, each balancing controller is configured to control a differentcircuit for balancing a different subset of the plurality of cell groupsand each stack controller is configured to control a different subset ofthe plurality of balancing controllers. The balancing circuit may alsoinclude a power supply configured to deliver power to the plurality ofstacks, a battery management system (BMS) configured to control powerdistribution to the plurality of cell groups by controlling theplurality of stack controllers, and an energy management system (EMS)configured to control power delivery by the power supply.

In another embodiment, a further balancing circuit is provided. Thebalancing circuit includes a plurality of cell groups and a plurality ofcell group controllers configured to control a different cell balancerelay for coupling a different cell group to the balancing circuit. Thebalancing circuit further includes a plurality of balancing controllersconfigured to control charging and discharging for a different subset ofthe plurality of cell groups. The balancing circuit also includes aplurality of string controllers configured to control a different subsetof the plurality of balancing controllers and a battery managementsystem configured to control power distribution in the balancing circuitby controlling the plurality of string controllers. The balancingcircuit may also include an energy management system configured tocontrol power delivery to the balancing circuit.

The foregoing and other objects, features, and advantages of theinvention will become more apparent from the following detaileddescription, which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example balancing circuit with whichone or more of the approaches described herein may be implemented.

FIG. 2 is a diagram illustrating another example balancing circuit withwhich one or more of the approaches described herein may be implemented.

FIG. 3 is a diagram illustrating yet another example balancing circuitwith which one or more of the approaches described herein may beimplemented.

FIG. 4 is a flowchart of an example embodiment for balancing cell groupsbased on a balancing profile.

FIG. 5 is a flowchart of an example embodiment for performing abalancing technique for balancing cell groups based on a user selectedbalancing application.

FIG. 6 is a flowchart of another example embodiment for performing abalancing technique for balancing cell groups based on a user selectedbalancing application.

DETAILED DESCRIPTION I. General Considerations

Disclosed below are representative embodiments of methods, apparatus,and systems for a battery cell balancing system and implementing abattery cell balancing strategy. The disclosed methods, apparatus, andsystems should not be construed as limiting in any way. Instead, thepresent disclosure is directed toward all novel and nonobvious featuresand aspects of the various disclosed embodiments, alone or in variouscombinations and subcombinations with one another. Furthermore, anyfeatures or aspects of the disclosed embodiments may be used in variouscombinations and subcombinations with one another. For example, one ormore system components or method acts from one embodiment may be usedwith one or more system components or method acts from anotherembodiment, and vice versa. The disclosed methods, apparatus, andsystems are not limited to any specific aspect or feature or combinationthereof, nor do the disclosed embodiments require that any one or morespecific advantages be present or problems be solved.

Although the operations of some of the disclosed methods are describedin a particular, sequential order for convenient presentation, it shouldbe understood that this manner of description encompasses rearrangement,unless a particular ordering is required by specific language set forthbelow. For example, operations described sequentially may in some casesbe rearranged or performed concurrently. Moreover, for the sake ofsimplicity, the attached figures may not show the various ways in whichthe disclosed methods may be used in conjunction with other methods.Additionally, the description sometimes uses terms like “determine,”“generate” and “evaluate” to describe the disclosed technology. Theseterms are high-level abstractions of the actual operations that areperformed. The actual operations that correspond to these terms may varydepending on the particular implementation and are readily discernibleby one of ordinary skill in the art.

Various alternatives to the examples described herein are possible. Forexample, some of the methods described herein may be altered by changingthe ordering of the method acts described, by splitting, repeating, oromitting certain method acts, etc. The various aspects of the disclosedtechnology may be used in combination or separately. Differentembodiments use one or more of the described innovations. Some of theinnovations described herein address one or more of the problems notedin the background. Typically, a given technique/tool does not solve allsuch problems.

As used in this application and in the claims, the singular forms “a,”“an,” and “the” include the plural forms unless the context clearlydictates otherwise. Additionally, the term “includes” means “comprises.”Further, as used herein, the term “and/or” means any one item orcombination of any items in the phrase.

II. Introduction to the Disclosed Technology

One or more the present embodiments provide for a battery cell balancingsystem and strategy that delivers more efficient use of batterycapacities as needed for different use cases. For example, a balancingcircuit is provided to support targeted battery cell passive and activebalancing according to a balancing strategy. Further the balancingcircuit allows for balancing to be performed while the battery cells arecollectively being charged or discharged for the application use case.

Further, in certain embodiments, instead of having a static, singlebalancing strategy, a suite of preset and customizable balancingapplications is provided that can be configured, selected and/orimplemented to match the requirements an application use case. The suiteof preset and customizable balancing applications may be presented toand selected by a user to tailor the balancing system to a particularuse case. Alternatively, the balancing system may automatically select abalancing application based on one or more inputs to tailor thebalancing system to the use case.

III. Example Embodiments

The embodiments discussed below provide and/or utilize a balancingcircuit to balance a plurality of battery cells or battery cell groups.For example, the balancing circuit may be provided as a circuitdedicated to balancing. One or more balancing strategies may beimplemented using the balancing circuit, allowing for selecting abalancing strategy that is specifically tailored to a use caseapplication. For example, a mix of passive balancing and target chargingcan be used to charge and/or discharge balance the plurality of batterycells or battery cell groups. Implementing the selected balancingstrategy allows for the battery cells to more efficiently andeffectively satisfy the requirements of the use case application whileincreasing safety and lifespan of the battery cells.

A. Example Systems

FIG. 1 is a schematic block diagram illustrating an example balancingcircuit with which one or more of the approaches described herein may beimplemented. The balancing circuit may be implemented in a largerbattery cell balancing system configured to implement a balancingstrategy to deliver more efficient battery usage as needed for differentuse cases. For example, depending on the use case, single battery cellsmay be targeted for passive and active balancing. Further, the targetedpassive and active balancing may be provided while the battery cells arein use (e.g., the battery cells are being charged or discharged).

With reference to FIG. 1 , the balancing circuit 100 illustratescomponents of a battery pack. For example, the balancing circuit (100)includes a voltage source (102) and a load (104). The voltage source(102) is any voltage source capable of charging battery cells, such as abalancing charger. For example, the voltage source (102) is a batterycharger configured to convert alternating current to direct current forcharging a battery cell or battery cell group. The voltage source (102)can also be configured to convert three-phase to single-phasealternating current. The voltage source can be coupled to a generator,such as in conjunction with a renewable energy source or coupled to anenergy grid or microgrid, such as via an inverter or an AC power supply.The load (104) is any electrical load, such as a resistor, inductor,capacitor, another component, or a combination of components acting asan electrical load for consuming electric energy.

The voltage source (102) is coupled to the balancing circuit (100) via acharge balancing relay (106) and the load (104) is coupled to thebalancing circuit (100) via a discharge balancing relay (108). Thecharge balancing relay (106) is configured to selectively couple thevoltage source (102) to the balancing circuit (100) for charging abattery cell or cell group. Likewise, the discharge balancing relay(108) is configured to selectively couple the load (104) to thebalancing circuit (100) for discharging a battery cell or cell group. Aswill be discussed below, the voltage source (102) or the load (104) isconnected or disconnected from the balancing circuit (100) to facilitatea charge balancing configuration, a discharge balancing configuration,or a no balancing configuration.

For example, the voltage source (102) and load (104) may be provided ata higher level than the battery cells, such as at the same control levelas the balancing controller (116) (discussed below). In an embodiment,the voltage source (102) is coupled to the balancing circuit (100) via adouble-pole, single throw (DPST) charge relay (106). When the chargerelay (106) is closed, the voltage source (102) may charge a cell groupcoupled to the balancing circuit (100). Likewise, the load (104) iscoupled to the balancing circuit (100) through a DPST discharge relay(108). When the discharge relay (108) is closed, the load (104) maydischarge a cell group coupled to the balancing circuit (100).

In the example illustrated in FIG. 1 , the voltage source (102) or theload (104) is configured to be coupled to the charge balancing circuit(100) in series. Therefore, at any point in time, the charge balancingcircuit (100) may be configured to either charge or discharge onebattery cell or cell group during that time. In other embodiments, thevoltage source (102) or the load (104) is configured to be coupled tothe charge balancing circuit (100) in a manner allowing for concurrentlycharging one battery cell or cell group while discharging a differentbattery cell or cell group.

The charge balancing circuit (100) includes a plurality of cell groupcontrollers (110(1), 110(2), . . . , 110(N)). For example, the cellgroup controllers are (110(1), 110(2), . . . , 110(N)) are batterymodule controllers (BMCs) or like controllers. Each of the cell groupcontrollers (110(1), 110(2), . . . , 110(N)) is configured to couple oneof a plurality of cell groups (114(1), 114(2), . . . , 114(N)) to thebalancing circuit (100) via one of a plurality of cell group balancingrelays (112(1), 112(2), . . . , 112(N)). Each of the cell groups(114(1), 114(2), . . . , 114(N)) includes one or more battery cells. Thebattery cells can be lithium-ion batteries or another known or futurebattery cell type. As will be discussed below, the battery cell groupsmay be implemented as a battery cell stack, including a stringcontroller (discussed below), a plurality of balancing controllers, aplurality of cell group controllers, a plurality of cell group relaysand a plurality of cell groups.

In an embodiment, the cell group controllers (110(1), 110(2), . . . ,110(N)) are implemented on a circuit board (e.g., a printed circuitboard) with the cell group balancing relays (112(1), 112(2), . . . ,112(N)). On each circuit board, the cell group balancing relays (112(1),112(2), . . . , 112(N)) may be implemented as double-pole, single throw(DPST) relays for each cell group. In this example, when a cell groupbalancing relay is closed, the relay attaches that cell group to thebalancing circuit (100). Additional or different relays may be used.Further, additional or different components can be included on thecircuit board, such as a balancing controller (discussed below) or oneor more microprocessors, microcontrollers, FPGAs, and/or ASICsconfigured to perform the disclosed behaviors.

In addition to controlling cell group balancing relays (112(1), 112(2),. . . , 112(N)), each of the cell group controllers (110(1), 110(2), . .. , 110(N)) is configured to measure voltage, temperature and otherinformation for its corresponding cell group. The cell group controllers(110(1), 110(2), . . . , 110(N)) are also configured to transmit themeasured voltage, temperature and other information to a balancingcontroller (discussed below) or to another control system coupled to thebalancing circuit (100).

The charge balancing circuit (100) also includes a balancing controller(116). For example, the balancing controller (116) is a battery packcontroller (BPC) or a like controller. The balancing controller (116)can be implemented by one or more microprocessors, microcontrollers,FPGAs, and/or ASICs. In this embodiment, the balancing controller (116)is responsible for implementing the balancing strategy. For example, thebalancing controller (116) is configured to balance the plurality ofcell groups (114(1), 114(2), . . . , 114(N)) by controlling the chargebalancing relay (106), the discharge balancing relay (108) and theplurality of cell controllers (110(1), 110(2), . . . , 110(N)). Further,by controlling by controlling the charge balancing relay (106), thedischarge balancing relay (108) and the plurality of cell controllers(110(1), 110(2), . . . , 110(N)), the balancing controller (116) maytarget specific cell groups independently with passive or activebalancing techniques. The balancing controller (116) can also beconfigured to aggregate data received from the plurality of cell groupcontrollers (110(1), 110(2), . . . , 110(N)), such as measured voltage,temperature and other information for each of the cell groups (114(1),114(2), . . . , 114(N)), and to store or buffer the data in volatilememory (e.g., registers, cache, RAM) or non-volatile memory (e.g., ROM,EEPROM, flash memory, etc.). The balancing controller (116) may then usethe aggregated data to make balancing decisions for the charge balancingcircuit (100).

In an embodiment, the balancing controller (116) is configured tobalance the plurality of cell groups (114(1), 114(2), . . . , 114(N))based on an external configuration in conjunction with the measuredvoltage, temperature and other information received from each of theplurality of cell group controllers (110(1), 110(2), . . . , 110(N)). Inone example, the external configuration includes a discharge balancingconfiguration, a charge balancing configuration, or a no balancingconfiguration. Additional and/or different external configurations maybe provided.

In the example provided above, three balancing configurations may beused in balancing the cell groups (114(1), 114(2), . . . , 114(N)). Thebalancing configurations may be referred to as balancing states,including a discharge balancing state, a charge balancing state, or a nobalancing state. In this example, at any given time, only one balancingconfiguration is implemented. As such, only one of the charge relay(106) or the discharge relay (108) may be closed at a time, or thecharge relay (106) and the discharge relay (108) may both be open.

In an example, a charge balancing configuration may include setting thecharge balancing relay (106) closed, setting the discharge balancingrelay (108) open, setting one of the cell group balancing relays(112(1)) closed, and setting the other cell group balancing relays(112(2), . . . , 112(N)) open. In this configuration, an individual cellgroup (112(1)) is charged, such as to a target balancing voltage.Likewise, a discharge balancing configuration may include setting thecharge balancing relay (106) open, setting the discharge balancing relay(108) closed, setting one of the cell group balancing relays (112(1))closed and setting the other cell group balancing relays (112(2), . . ., 112(N)) open. In this configuration, an individual cell group isdischarged, such as to a target balancing voltage. Finally, a nobalancing configuration may include setting the charge balancing relay(106) open, setting the discharge balancing relay (108) open and theplurality of the cell balancing relays (112(1), 112(2), . . . , 112(N))open. In this configuration, no cell groups are charged or discharged.

In an embodiment, to facilitate the aforementioned charge balancingconfigurations, balancing permissions may be provided, such as by ahigh-level control system (discussed below). For example, a chargebalancing permission may include a flag input indicating whether thebalancing controller (116) is permitted to charge. If the flag is set tofalse, the balancing controller (116) is not allowed to close the chargebalancing relay (106). Similarly, a discharge balancing permission mayinclude a flag input indicating whether the balancing controller (116)is permitted to discharge. If the flag is set to false, then thebalancing controller (116) is not allowed to close the dischargebalancing relay (106). Additional and different permissions may beprovided, such as to facilitate additional or different externalconfigurations. The high-level control system for setting the permissionflags may include battery management system (BMS), an energy managementsystem (EMS), or another high-level control system component, as will bediscussed below with respect to FIG. 2 .

FIG. 2 is a diagram illustrating another example balancing circuit withwhich one or more of the approaches described herein may be implemented.The balancing circuit may be implemented in a larger battery cellbalancing system configured to implement a balancing strategy to delivermore efficient battery usage as needed for different use cases. Forexample, depending on the use case, one or more battery cells may betargeted for passive and active balancing. Further, the targeted passiveand active balancing may be provided while the battery cells are in use(e.g., the battery cells are being charged or discharged).

With reference to FIG. 2 , the balancing circuit (200) includes aplurality of cell group stacks (220(1), 220(2), . . . , 220(N)). Eachcell group stack includes a plurality of battery packs within eachstack, as discussed above with respect to FIG. 1 . For example, eachbattery pack includes a voltage source (102) and a load (104). Thevoltage source (102) is any voltage source capable of charging batterycells. Alternatively, the voltage source (102) is one of a plurality ofvoltage sources, such as a plurality of battery chargers configured todistribute electric power to a different cell group stack (discussedbelow). In this example, the voltage source (102) is coupled to powersupply (226), as depicted in FIG. 2 . For example, the power supply(226) may be coupled to an energy grid and configured to convertalternating current to direct current for charging battery cell groups.Alternatively, the power supply (226) may be configured to provide ACpower to the voltage sources (102), with the voltage sources (102)configured to convert alternating current to direct current.Accordingly, the power supply (226) is configured to deliver electricpower to the plurality of cell group stacks. As discussed, AC power isprovided via the power supply (226). Alternatively, a DC power supply,an inverter, or one or more of the battery cells may be configured todeliver electric power to the plurality of cell group stacks, in lieu orin addition to the power supply (226). In one example, DC power from oneor more of the battery cells is delivered to one or more other batterycells for balancing. The load (104) is any electrical load, such as aresistor or another component acting as an electrical load for consumingelectric energy. In this embodiment, different battery packs may besimultaneously charged and/or discharged independent of the otherbattery packs.

In an alternative embodiment, each cell group stack (220(1), 220(2), . .. , 220(N)) includes a dedicated charge relay (106) and dedicated adischarge relay (108) for the stack. Likewise, each stack may alsoinclude dedicated voltage sources (102) and loads (104). In thisembodiment, different stacks cell group stack (220(1), 220(2), . . . ,220(N)) may be simultaneously charged and/or discharged independent ofthe other stacks.

The balancing circuit (200) includes a plurality of cell group stacks(220(1), 220(2), . . . , 220(N)). Each cell group stack (220(1), 220(2),. . . , 220(N)) includes a plurality of cell groups, such as cell groups(114(1), 114(2), . . . , 114(N)), a plurality of cell group relays, suchas relays (112(1), 112(2), . . . , 112(N)), a plurality of cell groupcontrollers, such as cell group controllers (110(1), 110(2), . . . ,110(N)), and a plurality of balancing controllers, such as balancingcontroller (116). In a particular embodiment, each stack includesseventeen (17) balancing controllers, but each stack can includeadditional or fewer balancing controllers. In the embodiment withseventeen (17) balancing controllers, each stack would also haveseventeen (17) charge relays (106) and seventeen (17) discharge relays(108). Each balancing controller is configured to control a differentcircuit for balancing a different subset of the plurality of cell groupsvia a different subset of cell group controllers and cell group relays.In an alternative embodiment, the cell group stacks (220(1), 220(2), . .. , 220(N)) do not include cell group controllers, and the plurality ofcell group relays are controlled directly by the balancing controllers.

The balancing circuit (200) further includes a plurality of stackcontrollers (218(1), 218(2), . . . , 218(N)). For example, the stackcontrollers (218(1), 218(2), . . . , 218(N)) are configured as stringcontrollers. The stack controllers (218(1), 218(2), . . . , 218(N)) areeach configured to control a different subset of balancing controllers.

In an embodiment, the balancing circuit (200) also includes a batterymanagement system (BMS) (222) and/or an energy management system (EMS)(224). The BMS (222) is configured to control power distribution to theplurality of cell groups by controlling the plurality of stackcontrollers (218(1), 218(2), . . . , 218(N)). The EMS (224) isconfigured to control power delivery by the power supply (226). The BMS(222) and EMS (224) are high-level control systems for balancing thestacks (220(1), 220(2), . . . , 220(N)). In an example, the BMS (222)and/or EMS (224) are implemented as software control systems on a servercomputer or within another computing environment, such as a virtualmachine environment. For example, the BMS (222) and the EMS (224) can beimplemented on one or more server computers, such as computer platformshaving hardware that includes one or more central processing units(CPU), a system memory, a random-access memory (RAM) and input/output(I/O) interface(s). The BMS (222) and EMS (224) can be implemented on asingle server computer or on a single computing environment.Alternatively, the BMS (222) and EMS (224) may be implemented on asingle controller or on multiple controllers.

To implement a balancing strategy, each of the plurality of stackcontrollers (218(1), 218(2), . . . , 218(N)) is configured to operatebased on a balancing mode, or external configuration, received from theBMS (222). For example, the balancing mode may include a target voltagemode for the cell groups within each cell group stack (220(1), 220(2), .. . , 220(N)). In the target voltage mode, cell group voltages arebalanced based on the target voltage for the cell groups.

In an embodiment, the balancing controllers for each stack areconfigured to determine the balancing target voltage for each stack.Alternatively, the balancing controllers are configured to receive atarget voltage from the stack controllers (218(1), 218(2), . . . ,218(N)), from the BMS (222), from the EMS (224), or from anothercomponent, and to balance each stack based on the received targetvoltage. Along with the target voltage, the balancing controllers may beconfigured to receive a balancing strategy for balancing based on thetarget voltage for each stack.

For example, the balancing controller determines the balancing targetvoltage as a voltage that the balancing controller will attempt tocharge and/or discharge all cell groups to match the target voltage.Referring back to the permissions discussed above, if the chargebalancing permission flag is set to be true, any cell below the targetvoltage will be charge balanced. If the discharge balancing permissionflag is set to be true, any cell below the target voltage will bedischarge balanced.

The target voltage may be determined based on different cell groupand/or cell group stack values. For example, the target voltage may beset as an average of the cells in a cell group, cell group stack orbattery pack. Alternatively, the target voltage may be set as a fixedvalue. In another alternative, the target voltage may be set as thelowest voltage or the highest voltage of a cell in a cell group, cellgroup stack or battery pack. A target voltage type may be set, based onwhich of the above values are used for determining the target voltage.

For example, the target voltage type may be set to an average, fixed,lowest or highest. Additional and different target voltage types may beprovided based on different cell group and/or cell group stack values,or based on other balancing metrics. The balancing controller may beconfigured to ignore saved target values that are not being used for thebalancing strategy. For example, when a fixed target voltage type isutilized, the average, lowest and highest target voltages are ignored.Likewise, if the voltage type is average, lowest, or highest, the fixedtarget voltage is ignored.

In addition to the target voltages, some embodiments include dead-bandvoltages that may be set within the balancing controllers and/ordetermined by the balancing controllers. For example, a charge balancingvoltage dead-band may be set. Based on the charge balancing voltagedead-band, cell group voltages that are greater than the dead-band value(e.g., number of millivolts below the balancing target voltage) do notrequire balancing and will not be charged. Likewise, a dischargebalancing voltage dead-band set, providing for cell group voltages thatare greater than the dead-band value (e.g., number of millivolts abovethe balancing target voltage) do not require balancing and will not bedischarged. The dead-band voltages may be modified according to thebalancing strategy, such as the cell voltages approach a maximum orminimum voltage. For example, the dead-band voltages may be modified toprevent the battery cells from being overcharged or undercharged (e.g.,for safety, longevity, etc.). Further, the dead-band values may bemodified to make a balancing strategy more or less aggressive.

As discussed above, to implement a balancing strategy, each of theplurality of stack controllers (218(1), 218(2), . . . , 218(N)) isconfigured to operate based on a balancing mode, or externalconfiguration, such as received from the BMS (222). In an embodiment,the balancing mode may be an average target voltage mode, a fixed targetvoltage mode, a low target voltage mode, a high target voltage mode, acharge voltage dead-band mode and a discharge dead-band mode. Additionaland different balancing modes may be provided.

To implement the average target voltage mode, the stack controllers willinstruct the balancing controllers to charge, to discharge, or to chargeand discharge individual cell groups to an average voltage all cellgroups. To implement the fixed target voltage mode, the stackcontrollers are configured to instruct the balancing controllers tocharge and/or discharge individual cell groups to a a fixed voltage forall cell groups. To implement the low target voltage mode, the stackcontrollers are configured to instruct the balancing controllers tocharge and/or discharge individual cell groups to a lowest voltage ofthe cell groups. To implement the high target voltage mode, the stackcontrollers are configured to instruct the balancing controllers tocharge and/or discharge individual cell groups to a highest voltage ofthe cell groups. To implement the charge voltage dead-band mode, thestack controllers are configured the instruct the balancing controllersto implement one of the above modes, but to ignore cell groups withvoltages less than a threshold below the target voltage. To implementthe discharge voltage dead-band mode, the stack controllers areconfigured to instruct the balancing controllers to ignore cell groupshaving voltages greater than a threshold above the target voltage.

FIG. 3 is a diagram illustrating yet another example balancing circuitwith which one or more of the approaches described herein may beimplemented. The balancing circuit may be implemented in a largerbattery cell balancing system configured to implement a balancingstrategy to deliver more efficient battery usage as needed for differentuse cases. For example, depending on the use case, one or more batterycells may be targeted for passive and active balancing. Further, thetargeted passive and active balancing may be provided while the batterycells are in use (e.g., the battery cells are being charged ordischarged).

With reference to FIG. 3 , the balancing circuit (300) includes aplurality of cell groups (314) and a plurality of cell group controllers(310). Each cell group controller (310) is configured to control adifferent cell balance relay, such as cell group relays (112(1), 112(2),. . . , 112(N)), for coupling a different cell groups (314) to thebalancing circuit (300), as discussed above. The balancing circuit (300)also includes a plurality of balancing controllers (316). Each balancingcontroller (316) is configured to control charging and discharging for adifferent subset of the plurality of cell groups (314). The balancingcontroller likewise includes a plurality of string controllers (318).Each string controller (318) is configured to control a different subsetof the plurality of balancing controllers (316). Accordingly, the cellgroup controllers (310), the balancing controllers (316) and the stringcontrollers (318) are provided for low-level control of the cell groups(314) of the balancing circuit (300).

In an embodiment, the balancing circuit (300) may also includehigh-level control for the cell groups (314). For example, the balancingcircuit (300) includes a battery management system (BMS) (322)configured to control power distribution in the balancing circuit (300)by controlling the plurality of string controllers (318). By controllingthe string controllers (313), the BMS ultimately has control over thecell group controllers (310) and power distribution to the cell groups(314). Accordingly, the BMS (322) controls power distribution within thebalancing circuit (300) by charging and/or discharging specific cellgroups of the cell groups (314) via the plurality of cell groupcontrollers (310), the plurality of balancing controllers (314) and theplurality of string controllers (318).

In another embodiment, the balancing circuit (300) also includes anenergy management system configured to control power delivery to thebalancing circuit. For example, while the BMS (322) controls powerdistribution in the balancing circuit (300), the EMS (324) controlspower input to the balancing circuit (300). The EMS (324) is configuredto control power distribution by controlling an inverter, such as powersupply (226), and/or a voltage source, such as voltage source (102).

The aforementioned components of the balancing circuits 100, 200 and 300are configured to be coupled together and communicate via softwareapplication programming interfaces (APIs) and/or via known or futurecommunication protocols. For example, communication may be facilitatedusing Modbus, CANbus, DNP3, web services interface or another protocoland to utilize APIs to communicate between components of like anddifferent control levels. In an embodiment, the BMS (322) is configuredto communicate with the string controllers (316) via a ModBus API oranother balancing application API. In this embodiment, the API exposesor virtually couples a set of ModBus communication points (e.g.,MESA-ESS (Energy Storage System) and SunSpec compatible) allowing forthe activation and configuration of all balancing applications ofdownstream components, reporting of current settings, and reporting ofcurrent battery states and the impact of the balancing applications.

As discussed above, the balancing controllers (316) are configured tooperate in a plurality of balancing states or configurations. Forexample, the balancing controllers are configured to operate in one ormore of a charge balancing state for charging cell groups (314) to atarget voltage, a discharge balancing state for discharging cell groups(314) to a target voltage, or a no balancing state for decoupling cellgroups (314) from the balancing circuit (300). In the no balancingstate, no cell groups (314) are charged or discharged for the purposesof balancing. In an embodiment, when balancing controllers (316)transition between charge balancing and discharge balancing states, ortransition between charging or discharging different cell groups (314),the balancing controllers transition to the no balance before chargingor discharging the different cell group (314).

Further, at any time, the balancing controllers (316) may execute one ofmany behaviors. In an embodiment, the balancing controllers (316) mayoperate in one of three behaviors: balance monitoring; charge balancing;or discharge balancing. As discussed above, in an embodiment, whentransitioning from one behavior to the next (e.g., charge balancing todischarge balancing), the balancing controllers will transition throughthe no balancing or a balance monitoring state. For example, in a nobalancing or balance monitoring state, all relays must be opened, andall cell groups must confirm that all cell group relays are open beforeproceeding with charging or discharging a cell group by closing anyrelays. In an embodiment, the balancing controllers must also transitionthrough the no balancing or balance monitoring state even if thebehavior remains the same (i.e., transitioning from charge balancing onecell group to another cell group). In this example, if the balancingcontroller transitions from charge balancing a first cell group tocharge balancing second cell group, balancing controller will: (1)transition from a charge balancing state to a no balancing state; (2)confirm that all relays are open; and (3) transition from the nobalancing state back to the charge balancing state. By transitioning tothe no balancing state between charge/discharge balancing states, thebalancing controller may provide for safe and reliable operations.

During balance monitoring, a balancing controller monitors each cellgroup assigned to the balancing controller to determine which cells, ifany, need balancing. In an embodiment, the balancing controller performsbalance monitoring by periodically calculating a balancing targetvoltage. The balancing target voltage may be based on the currentbalancing mode or a fixed balancing target voltage. The balancingcontroller may further calculate a balance offset voltage for each cellgroup as a voltage difference that each cell group sits from a dead-bandrange. Next, for the balancing controller to determine which cells needto be charged and/or discharged, the balancing controller determines ifeach cell voltage is above or below the balancing target voltage.

If a cell group voltage is above the balancing target voltage, then thebalancing controller may proceed in determining how to handle the cellgroup as follows. If the discharge balancing permission is set to false(e.g., discharge balancing is not permitted), all cell groups areignored for the purposes of discharge balancing. Next, if a cell groupvoltage is less than the discharge balancing dead-band (e.g., less thanthe balancing target voltage value plus a discharge balancing voltagedead-band value), then the cell group is also ignored. Finally, for theremaining cell groups (e.g., cell groups that are not ignored), abalancing offset is calculated for each cell group (e.g., cell groupvoltage less the balancing target voltage and the discharge balancingvoltage dead-band value).

If a cell group voltage is below the balancing target voltage, then thebalancing controller may proceed in determining how to handle the cellgroup as follows. If the charge balancing permission is set to false(e.g., charge balancing is not permitted), all cell groups are ignoredfor the purposes of charge balancing. Next, if a cell group voltage isgreater than the charge balancing dead-band (e.g., greater than thebalancing target voltage value less the charge balancing voltagedead-band value), then the cell group is also ignored. Finally, for theremaining cell groups (e.g., cell groups that are not ignored), abalancing offset is calculated for each cell group (e.g., the balancingtarget voltage less the discharge balancing voltage dead-band value andthe cell group voltage).

Based on the calculated balancing offset values, the balancingcontroller transitions into a balancing behavior. If no cell groups havea balancing offset (e.g., no cell group is outside of the dead-bandand/or has the appropriate position to balance based on thepermissions), then the balance monitoring process is repeated. However,when balancing offsets are calculated, the cell group with the highestbalance offset is selected for balancing. If the selected cell group hasa voltage above the balancing target voltage, then the balancingcontroller transitions to discharge balancing. If the selected cellgroup has a voltage below the balancing target voltage, then thebalancing controller transitions to charge balancing. After balancingthe selected cell group, the balancing controller may select anothercell group with the next highest balance offset for balancing andtransition accordingly.

During charge balancing, a balancing controller charges a cell group,such as by continuing to charge the cell group until the cell groupvoltage reaches a charge target voltage or another value. As discussedabove, a cell group with the highest offset value may be selected forcharging. For example, when the balancing controller transitions tocharge balancing, energy transmitted or injected into a selected cellgroup. Energy will continue to be transmitted until the selected cellgroup voltage is equal to the balancing target voltage. In anotherembodiment, the selected cell group will continue to be charged untilthe cell group voltage is within the cell balancing dead-band. Whilecharge balancing, the balancing controller may continue to calculate thebalancing target voltage and to determine if the charge balancing shouldhalt. For example, the charge balancing should halt if the chargebalancing permission becomes false or the cell group voltage becomesgreater than or equal to the balancing target voltage. If the chargebalancing is halted, the balancing controller transitions to balancemonitoring.

Likewise, during discharge balancing, a balancing controller dischargesa cell group, such as continuing to discharge the cell group until thecell group voltage reaches a discharge target voltage or another value.As discussed above, a cell group with the highest offset value may beselected for discharging. For example, when the balancing controllertransitions to discharge balancing, energy removed or dissipated from aselected cell group. Energy will continue to be removed until theselected cell group voltage is equal to the balancing target voltage. Inanother embodiment, the selected cell group will continue to bedischarged until the cell group voltage is within the cell balancingdead-band. While discharge balancing, the balancing controller maycontinue to calculate the balancing target voltage and to determine ifthe discharge balancing should halt. For example, the dischargebalancing should halt if the discharge balancing permission becomesfalse or the cell group voltage becomes less than or equal to thebalancing target voltage. If the discharge balancing is halted, thebalancing controller transitions to balance monitoring.

B. Example Applications and Usage Scenarios

As discussed above, instead of having a static, single balancingstrategy, one or more the present embodiments provide for multiplebalancing applications to be selected and implemented to match therequirements of the present use case. The balancing applications areselected to tailor the aforementioned balancing circuits to a particularuse case to employ a passive and active balancing strategy to moreefficiently and effectively satisfy the requirements of the use casewhile increasing safety and lifespan of the battery cells.

FIG. 4 is a flowchart of an example embodiment for balancing cell groupsbased on a balancing profile. The method can be implemented by any ofthe systems of FIGS. 1-3 and/or a different system. Additional,different or fewer acts may be provided. For example, various acts maybe omitted or performed by a separate system. Although the method ispresented in the illustrated order, other orders may be provided and/oracts may be repeated, such as repeating acts 410, 412 and 414 based onreceiving a different balancing profile.

At act 410, a balancing profile is received for balancing battery cellsin a balancing circuit. In an embodiment, a battery management system(BMS) or an energy management system (EMS) receives the balancingprofile via an application programming interface (API) from a userdevice, such as a mobile device or a workstation (328) coupled to theEMS, the BMS or another component of the balancing circuit (300). Theworkstation (328) may operate in a client-server implementation, whereinthe workstation (328) is remote from other components of the balancingcircuit (300). The workstation (328) may be implemented as a computerplatform having hardware that includes one or more central processingunits (CPU), a system memory, a random-access memory (RAM) andinput/output (I/O) interface(s).

For example, the workstation presents a predefined or user configurableset, library or menu of balancing profiles that may be enabled andconfigured for different use cases for the battery cells. In anotherembodiment, the balancing profile is received by the BMS from EMS, oranother control system component, to automatically select a balancingprofile based on a use case application of the battery cells. Asdiscussed above, the API may be implemented using known or futurecommunication protocols, such as Modbus, CANbus, DNP3, web servicesinterface or another protocol allowing the APIs to communicate betweencomponents of like and different control levels.

The balancing profiles may rely on balancing reporting from the stacksincluding the current state of the battery cell groups and the impact ofthe current balancing profile on the battery cells. Additionally,balancing profiles may be provided using a schedule. For example,balancing profiles may be implemented using the time-of-day, dates, andsets of stacks create balancing times for different stacks within thebalancing circuit. As such, the balancing schedule would be an overlayfor the balancing profiles, altering the functionality of the system tooptimize for time of use, efficiency, consumption needs and/or otherfactors. For example, battery cell groups are often deployed for solargeneration and configured to store the energy generated by solar cells.Solar generation follows a predictable schedule curve, and matching thebalancing strategy to the schedule curve may allow the balancingstrategy to be tuned appropriately (e.g., knowing that the battery cellswill likely charge slowly early in the day, that the battery cells willnot charge at night, etc.) Additionally, many other balancing strategiesand use case applications are schedule driven. For example, if aschedule requires maximum energy at a specific time during the day(e.g., participation in an energy market), then knowing that the batterycells must be fully charged at a specific time may be a critical inputto the balancing strategy.

In an embodiment, the library of predefined or user configurablebalancing profiles includes two or more of: a no balancing profile; abasic balancing profile; a full discharge optimizing profile; a fullcharge optimizing profile; a slow charge optimizing profile; a slowdischarge optimizing profile; and a high efficiency profile. Additionaland different balancing profiles may be included in the library. Forexample, the library of balancing profiles may further include one ormore additional balancing profiles defined to manage voltage differencesbetween cell groups based on additional or different use cases for thebattery cell groups.

For example, with reference to FIG. 3 , the BMS (322) includes a nobalancing profile that is configured to do no balancing at all. In otherwords, voltage differences between cell groups (314) are not minimized.As discussed above, the no balancing profile may be implemented when theBMS (322) transitions between balancing profiles.

The BMS (322) may also include a basic balancing profile that isconfigured to minimize voltage differences between cell groups bybalance cell groups by charging and/or discharging cell groups. Forexample, the basic balancing profile includes an out-of-balance triggervalue (e.g., in mV), an in-balance trigger value (e.g., in mV), and acell voltage dead-band (e.g., in mV). In this example, the balancingcontrollers (316) monitor cell groups (314) to determine if any cellgroups (314) have cell voltages outside of the cell voltage dead-band.Starting with the cell group with the highest difference with respect tothe average cell voltage for the cell groups (314), cell groups arecharged and/or discharged to equalize cell group voltages between allcell groups (314). Specifically, if the cell voltage spread between thecell group voltage and the average voltage for the cell groups isgreater than the out-of-balance trigger value, the cell group isactively or passive balanced until the cell group voltage is equal tothe average voltage for the cell groups or is within the in-balancetrigger value.

In another embodiment of a basic balancing profile, voltage differencesbetween cell groups are minimized irrespective of battery state ofcharge (SOC) values. As such, cell groups are charged or discharged ifthe cell group voltages are outside of a balancing dead-band around theaverage cell group voltage. In yet another embodiment, the basicbalancing profile is configured to balance the cell groups based ondead-band values. For example, based on the basic balancing profile, thebalancing controller identifies a subset of the cell groups withvoltages outside of the dead-band values, determines a cell group fromthe subset of cell groups as having the highest voltage difference froman average voltage of the cell groups, and charges or discharges thecell group. The balancing controller then repeats the process to balancethe cell group with the next highest voltage difference from the averagevoltage of the cell groups.

The BMS (322) may also include a full charge optimizing balancingprofile that is configured similarly to the basic balancing profile,however the full charge balancing profile only passively balances downcell groups that are above a dead-band value. In this example, the BMS(322) dynamically adjusts the dead-band to work the voltage kneeaggressively. For example, because the relationship between state ofcharge (SOC) (e.g., from 0% to 100%) and voltage is not a straight line,near the edges of the SOC range, a small change in SOC may require avery large change in voltage, resulting in an increased risk whenoperating a battery cell from the plateau through the knee of the curvebecause the battery cell may be accidently driven to a dangerously low(or high) voltage. Therefore, dynamically adjusting the dead-band as thebattery cells are charged from the plateau through the knee of the curvemay increase safety while aggressively charging the battery cells. Assuch, active balancing is only used for cell groups that are far outsidethe dead-band value and far from the average voltage that the cellgroups become dangerous. By dynamically adjusting the dead-band, batterycells well above or below the average are more aggressively balanced,allowing more of the knee area of the curve to be a usable SOC range.

In another embodiment, a full charge optimizing profile is configured tomanage cell voltage differences between cell groups in order to maximizethe battery SOC values by charging cell groups with lowest voltages. Inthis example, only cell groups with voltages above a high-chargethreshold are discharged. In yet another embodiment, a full chargeoptimizing profile is configured to balance cell group voltages up. Inthis example, only cell groups with voltages above a high-chargethreshold are balanced down and cell groups with voltages below the lowcharge dead-band are balanced up.

The BMS (322) may also include a full discharge optimizing balancingprofile that is configured similarly to the basic balancing profile,however the full discharge balancing profile only actively balances upcell groups that are below a dead-band value. Again, in this example,the BMS (322) dynamically adjusts the dead-band to work the voltage kneeaggressively. As such, passive balancing is only used for cell groupsthat are far outside the dead-band value and far from the averagevoltage that the cell groups become dangerous.

In another embodiment, a full discharge optimizing profile is configuredto manage voltage differences between cell groups in order to minimizethe battery SOC values by discharging cell groups with highest voltages.In this example, only cell groups with voltages below a low-chargethreshold are charged. In yet another embodiment, a full dischargeoptimizing profile is configured to balance cell group voltages down. Inthis example, only cell groups with voltages below a low-chargethreshold are balanced up and only cell groups with voltages above ofthe high discharge dead-band are balanced down.

The BMS (322) may also include a slow charge optimizing profile that isconfigured similarly to the basic balancing profile, however given atarget voltage, the voltage source is used to slowly raise all cells tothe target voltage. For example, the slow charge profile manages voltagedifferences between cell groups to increase battery SOC values bycharging or discharging cell groups with voltages outside of a chargedead-band. Further, the voltage charge dead-band is decreased as cellgroup voltages approach a high-charge threshold.

The BMS (322) may also include a slow discharge optimizing profile thatis configured similarly to the basic balancing profile, however given atarget voltage, the load is used to slowly raise all cells to the targetvoltage. For example, the discharge profile manages voltage differencesbetween cell groups to decrease cell group SOC values by charging ordischarging cell groups with voltages outside of an discharge dead-band.Further, the discharge dead-band is decreased as cell group voltagesapproach a low-charge threshold.

In an embodiment, a charge profile and a discharge profile areconfigured to balance cell group voltages up or down to a target voltageby charging or discharging cell groups with voltages outside of adead-band. Further, the dead-band is decreased as cell group voltagesapproach a high-charge threshold or a low-voltage threshold,respectively.

The BMS (322) may also include a high efficiency profile configured toimplement variants of the above balancing profiles that only balancecell groups up or down as cell group voltages to maintain maximumefficiency, such as when cell group voltages approach the voltage knees.For example, the high efficiency profile manages voltage differencesbetween cell groups in order to minimize charging and discharging of thecell groups, such as to minimize energy consumption and/or dissipation.In an embodiment, only cell groups voltages with voltages approachingthe high-charge threshold or the low-charge threshold are balanced.

In an embodiment, the high efficiency profile is configured to balancecell group voltages to a target voltage by minimizing the overallcharging and discharging the cell groups to consume and dissipate lessenergy than other balancing profiles, such as by minimizing energyconsumption and dissipation. For example, cell group voltages that arenot approaching a high-charge threshold or a low-charge threshold maynot be balanced.

Referring back to FIG. 4 , at act 412, a plurality of cell group stringcontrollers is controlled based on the received balancing profile. In anembodiment, the BMS controls the plurality of cell group stringcontrollers by instructing the string controllers to balancing eachbattery cell stack based on the balancing profile. As discussed above,each string controller is configured to control a different subset ofbalancing controllers.

At act 414, a plurality of cell balancing controllers is controlled bythe cell group string controllers based on the received balancingprofile. In an embodiment, each cell group balancing controller balancesa different plurality of cell groups. As discussed above, each balancingcontroller is configured to control a different subset of cell groupcontrollers to balance the cell groups. The cell group controllers,balancing controllers and string controllers provide for low-levelcontrol of the cell groups based on the received balancing controller.

Referring back to FIGS. 1-3 , exemplary cell group balancing systems areprovided. For example, with respect to FIG. 3 , a cell group balancingsystem may be implemented as the balancing circuit (300). The balancingcircuit (300) includes a plurality of cell groups (314) and a pluralityof cell group controllers (310). As discussed above, each of the cellgroup controllers (310) are configured for a different cell group of theplurality of cell groups (314). The balancing circuit (300) alsoincludes a plurality of balancing controllers (316) configured tocontrol a different subset of the plurality of cell group controllers(310) and a plurality of string controllers (318) configured to controla different subset of the plurality of balancing controllers (316). Inthis embodiment, the cell group controllers (310), the balancingcontrollers (316) and the string controllers (318) are provided forlow-level control of the cell groups (314) of the balancing circuit(300).

The balancing circuit (300) includes further includes a batterymanagement system (BMS) (322) configured to control the plurality ofstring controllers (318) and an energy management system (EMS) (324)configured to implement a balancing technique for balancing cell groupsbased on a user selected balancing application. The BMS (322) and theEMS (324) are provided for high-level control of the cell groups (314)of the balancing circuit (300). As discussed above, the aforementionedlow-level and high-level control components may communicate applicationprogramming interfaces (APIs), such as according to Modbus, CANbus,DNP3, web services interface or another communication protocol.

FIG. 5 is a flowchart of an example embodiment for performing abalancing technique for balancing cell groups based on a user selectedbalancing application. As discussed above, the method may be implementedby the system of FIGS. 1-3 and/or on a different system. Additional,different or fewer acts may be provided. For example, various acts maybe omitted or performed by a separate system. Although the method ispresented in the illustrated order, other orders may be provided and/oracts may be repeated, such as repeating acts 510, 512 and 514 based onre-presenting the menu and receiving a different user selectablebalancing application.

At act 510, a menu of user selectable balancing applications ispresented to a user. In an example, the user selectable balancingapplications are presented via a graphical user interface, such as at auser workstation. For example, the menu may include predefined balancingapplications, such as: a no balancing application; a basic balancingapplication; a full discharge optimizing application; a full chargeoptimizing application; a slow charge optimizing application; a slowdischarge optimizing application; and a high efficiency application.Further, the menu may include additional customizable balancingapplications. Additional and different balancing applications may beincluded in the library.

In one exemplary embodiment, a basic graphical user interface presents amenu to the user for controlling one or more stacks or battery packswithin the stacks to be targeted and provided with a balancing mode(e.g., no balancing, average target voltage mode, a fixed target voltagemode, a low target voltage mode, a high target voltage mode, a chargevoltage dead-band mode and a discharge dead-band mode, or another mode),a target voltage type (e.g., average, fixed, lowest, highest, or anothertype), an optional voltage target, permissions to charge/discharge cellgroups, charge and discharge dead-bands, and other balancing settings.As such, the basic graphical user interface may be configured for veryspecific control of individual balancing scenarios, such as in the caseof maintenance or operational events. In another embodiment, balancingapplication graphical user interface may be provided for higher levelbalancing applications for implementing a balancing strategy, such as byselecting a preconfigured balancing application (e.g., a no balancingapplication, a basic balancing application, a full discharge optimizingapplication, a full charge optimizing application, a slow chargeoptimizing application, a slow discharge optimizing application, a highefficiency application, or another application). In a furtherembodiment, a high-level graphical user interface is configured to pairbalancing applications with energy management applications. For example,an energy management application may be selected to implement a higherlevel balancing strategy (e.g., “charge battery to full by 4 AM”), whichis paired with an applicable balancing application (e.g., a full chargeoptimizing application, a slow charge optimizing application, a highefficiency application, or another application) based on the higherlevel balancing strategy. Additional and different graphical userinterfaces may be provided, and the aforementioned example interfacesmay be combined and/or used concurrently.

At act 512, a user selected balancing application is received from theuser. In an example, the user selected balancing application is receivedby the user workstation via the graphical user interface. The user mayselect the balancing application based on how the battery cells arebeing used. For example, different balancing applications may beselected for the different requirements of grid and microgrid energystorage and management, and for renewable energy integration. Forexample, during summer months, energy consumption increases dramaticallyduring daylight hours (e.g., as a result increased demand forair-conditioning, etc.). Accordingly, during evening hours, a fullcharge optimizing application may be selected to prepare for theincrease in demand for the following day. In another example, thebattery cells may be configured to provide for a full discharge at agiven time during the next day. Therefore, a balancing application maybe selected to drive the battery cells to a maximum SOC the night beforeduring a charge cycle, to keep the battery cells fully charged without apower supply during the lead-up period, and to provide for maximumdischarge during the given time the next day or during an event. In yetanother example, the battery cells may be configured to provide for abalanced frequency response at all times, using the entire SOC range.Accordingly, a balancing application may be selected to keep the balancethe battery cells to an average SOC, or as closely balanced as possible.Alternatively, the battery cells may be configured to provide for abalanced frequency response at all times, but only using a middle sliceof the SOC range (e.g., 20% to 80%). In that case, the balancingapplication may be selected for high energy efficiency, only balancingcells that were far out of range. In a further example, the batterycells may be configured to provide for unbalanced services during theday, with an expectation of full charging at night. As such, an averagebalancing application may be selected during the day, then a chargeoptimizing balancing application may be selected at night. Further, if acharge period was narrow (e.g., as with frequency responseapplications), a balancing application may be selected for quickcharging, and if the charge period was wide, the balancing applicationmay be selected for full charging. Additional and different use casesmay be provided, with one or more different balancing applicationsselected based on the use case.

At act 514, instructions for balancing the plurality of cell groups aretransmitted based on the user selected balancing application. In anexample, the instructions are transmitted via an application programminginterface (API) to one or more of the aforementioned low-level andhigh-level control components. As discussed above, balancing APIs areconfigured for communication between components in the balancing circuitto allow for the activating and configuring downstream components toimplement the selected balancing application, reporting of currentsettings, reporting of current battery states and reporting the impactof the balancing applications. In one or more embodiments, the API isconfigured to transmit the instructions for balancing the plurality ofcell groups to the balancing controllers. Additionally or alternatively,the API is configured to transmit the instructions for balancing theplurality of cell groups to the plurality of string controllers.Further, additionally or alternatively, the API is configured totransmit the instructions for balancing the plurality of cell groups tothe BMS and/or EMS.

As discussed above, the balancing applications may be implemented usinga schedule. For example, the selected balancing application may betailored to the time-of-day, date, and subset of stacks within thebalancing circuit. As such, the schedule may alter the functionality ofthe selected balancing application to optimize for time of use,efficiency, consumption needs and/or other factors.

FIG. 6 is a flowchart of another example embodiment for performing abalancing technique for balancing cell groups based on a user selectedbalancing application. The method is implemented by the system of FIGS.1-3 and/or a different system. Additional, different or fewer acts maybe provided. For example, various acts may be omitted or performed by aseparate system. Although the method is presented in the illustratedorder, other orders may be provided and/or acts may be repeated, such asrepeating acts 610, 612, 614 based on receiving a different balancingapplication.

At act 610, a balancing application is received based on a userselection from a library of balancing applications. In an embodiment,the balancing application is received by an energy management system(EMS). The EMS is configured to provide an application framework forconfiguring and managing of different balancing applications, compatiblewith existing balancing circuits. The balancing application is selectedfrom a library of balancing applications that includes multipleavailable predefined balancing applications configured for different usecases for the cell groups. Further, customizable balancing applicationsmay be selected to further configure an application to a use case forthe cell groups

At act 612, balancing instructions are generated by the EMS, by abattery management system (BMS) or by another high-level control systemcomponent based on the received balancing application. The instructionsare generated for implementing the balancing application on low-levelcontrol system components (e.g., string controllers, balancingcontrollers, cell group controllers and/or other controllers).

At act 614, the balancing instructions are transmitted for balancing thecell groups. In an embodiment, the instructions are transmitted fromhigh-level control components to low-level cell group control componentsvia an application programming interface (API).

At act 616, the cell groups are balanced based on the balancinginstructions. In this embodiment, the cell groups are balanced vialow-level cell group control components, as discussed above.

IV. Concluding Remarks

In view of the many possible embodiments to which the principles of thedisclosed invention may be applied, it should be recognized that theillustrated embodiments are only preferred examples of the invention andshould not be taken as limiting the scope of the invention. Rather, thescope of the invention is defined by the following claims. We thereforeclaim as our invention all that comes within the scope and spirit ofthese claims.

We claim:
 1. A balancing circuit comprising: a cell group stackcomprising: a plurality of cell groups; a plurality of cell groupbalancing relays, each of the cell group balancing relays electricallycoupled to one of the cell groups; a charge balancing relay configuredto selectively electrically couple a voltage source to the plurality ofcell group balancing relays; a discharge balancing relay configured toselectively electrically couple a load and the plurality of cell groupbalancing relays; and a balancing controller communicatively coupled tothe plurality of cell group balancing relays, the charge balancingrelay, and the discharge balancing relay, wherein the balancingcontroller controls open and closed states of the plurality of cellgroup balancing relays, charge balancing relay, and discharge balancingrelay based on a balancing state of the cell group stack.
 2. Thebalancing circuit of claim 1, further comprising one or more additionalcell group stacks and a power source arranged to deliver electricalpower to the cell group stacks.
 3. The balancing circuit of claim 2,further comprising a battery management system and a plurality of stackcontrollers, at least one of the stack controllers communicativelycoupled to the battery management system and at least one of the cellgroup stacks, the at least one of the stack controllers to control thebalancing controller of the at least one of the cell group stacks basedon an external configuration received from the battery managementsystem.
 4. The balancing circuit of claim 1, wherein the balancing stateof the cell group stack is selected from the group consisting of acharge balancing state, a discharge balancing state, and a no balancestate.
 5. The balancing circuit of claim 1, further comprising thevoltage source and the load.
 6. The balancing circuit of claim 1,wherein the balancing controller is configured to balance the pluralityof cell groups based on aggregated data for each of the cell groups. 7.The balancing circuit of claim 1, wherein the balancing controller isconfigured to balance the plurality of cell groups based on a measuredvoltage and a measured temperature received for each of the cell groups.8. A balancing circuit comprising: a plurality of cell groups; aplurality of cell balance relays; a plurality of balancing controllers,each balancing controller configured to control charging and dischargingfor a different subset of the plurality of cell groups; a plurality ofstring controllers, each string controller configured to control adifferent subset of the plurality of balancing controllers; and abattery management system configured to control power distribution inthe balancing circuit by controlling the plurality of stringcontrollers, wherein each balancing controller controls open and closedstates of a subset of the plurality of cell balance relays based on abalancing state of the balancing controller.
 9. The balancing circuit ofclaim 8, further comprising: an energy management system configured tocontrol power delivery to the balancing circuit.
 10. The balancingcircuit of claim 9, wherein the energy management system is configuredto control power delivery from a power supply based upon a balancingprofile received via an application programming interface (API) from auser device.
 11. The balancing circuit of claim 8, wherein the balancingstate of each of the balancing controllers is one of in a plurality ofstates comprising: a charge balancing state for charging one of theplurality of cell groups to a target voltage; a discharge balancingstate for discharging one of the plurality of cell groups to a targetvoltage; and a no balance state for decoupling a subset of the pluralityof cell groups from the balancing circuit.
 12. The balancing circuit ofclaim 11, wherein the balancing controllers are configured to transitionto the no balance state before charging or discharging a different cellgroup.
 13. The balancing circuit of claim 8, wherein the balancingcircuit is configured to charge or discharge specific cell groups of theplurality of cell groups via the plurality of balancing controllers andthe plurality of string controllers.
 14. A balancing circuit comprising:a plurality of cell group stacks, each stack comprising: a plurality ofcell groups; and a plurality of balancing controllers, each balancingcontroller configured to control a different circuit for balancing adifferent subset of the plurality of cell groups; and a plurality ofstack controllers, each stack controller configured to control adifferent subset of the plurality of balancing controllers.
 15. Thebalancing circuit of claim 14, further comprising: a power supplyconfigured to deliver power to the plurality of cell group stacks; abattery management system (BMS) configured to control power distributionto the plurality of cell groups by controlling the plurality of stackcontrollers; and an energy management system (EMS) configured to controlpower delivery by the power supply.
 16. The balancing circuit of claim15, wherein each of the plurality of stack controllers is configured tooperate based on a balancing mode received from the BMS, wherein thebalancing mode comprises a target voltage mode for equalizing voltagesof the plurality of cell groups.
 17. The balancing circuit of claim 16,wherein the target voltage mode comprises: an average mode configured tocharge, to discharge, or to charge and discharge one or more of theplurality of cell groups to a target voltage set to an average voltageof the plurality of cell groups; or a fixed target voltage modeconfigured to charge, to discharge, or to charge and discharge one ormore of the plurality of cell groups to a target voltage set as a fixedvoltage for the plurality of cell groups.
 18. The balancing circuit ofclaim 16, wherein the target voltage mode comprises: a low targetvoltage mode configured to charge, to discharge, or to charge anddischarge one or more of the plurality of cell groups to a targetvoltage set to a lowest voltage of the plurality of cell groups; or ahigh target voltage mode configured to charge, to discharge, or tocharge and discharge one or more of the plurality of cell groups to atarget voltage set to a highest voltage of the plurality of cell groups.19. The balancing circuit of claim 16, wherein the balancing modeincludes a charge voltage dead-band configured to ignore cell groupswith voltages less than a threshold below a target voltage.
 20. Thebalancing circuit of claim 16, wherein the balancing mode includes adischarge voltage dead-band configured to ignore cell groups havingvoltages greater than a threshold above a target voltage.